Abstract: Towards a Wireless Implantable Intracranial Ultrasound (wICUS) Imaging System Brain imaging is crucial in detection of congenital abnormalities in anatomical brain structures, for instance in hydrocephalus, brain masses, determining the presence or severity of hemorrhage in the brain, assessment of brain damage, inflammation or trauma, status of brain tumors before, during, and after surgical removal or chemotherapy and many other emerging applications. Computer tomography (CT) and magnetic resonance imaging (MRI) have been the major brain imaging modalities so far. However, because of their dependency upon ionizing radiation and very strong magnetic field, respectively, their exposure limits and requirement of sophisticated, costly, and delicate equipment plus slow and time consuming procedures are not likely to abate anytime soon. Therefore, there is an ever-growing search for new imaging modalities that would be more cost-effective, smaller and more portable, higher resolution, and even continuous. Ultrasound is one of the most widely used medical diagnostic imaging modalities, which is broadly used to image and characterize soft tissue and blood flow at various depths and resolutions. Despite all this, except in infants, it has largely shied away from the brain, predominantly because of the poor penetration of ultrasonic waves through the bone, into and out of the adult skull at imaging frequencies. We propose to take the first steps in changing the status quo by creating a ?wireless Implantable Intracranial Ultrasound (wICUS) imaging system,? which will be located inside the cranial cavity, above dura matter, bypassing the skull bone attenuation and distortion, as in intra-operative ultrasound, but it will provide on-demand imaging capability over time and post-operation on awake and ambulatory patients until its removal. We will create a stack of a highly miniaturized 2D ultrasonic transducer array on a system-on-a-chip (SoC) integrated circuit carrying all the necessary interface electronics, wireless power, and data transmission coils and antennas, needed to operate from inside the cranial cavity, under the skull, packaged in the form of a planar implant about the size of a quarter. wICUS will be located above dura matter, bypassing the skull bone attenuation and distortion, and powered wirelessly through an efficient resonant-based 3-coil inductive link across the scalp and skull in the industrial scientific medical (ISM) band, capable of safely delivering up to 100 mW over the period of imaging (5~30min). A bidirectional data link will be established with wICUS to deliver imaging configuration commands, downlink towards the implant. The uplink data from the implant to an external receiver (RF-Rx), which needs to be considerably more wideband, will use an ultra low power impulse radio transmitter (RF-Tx) in the near-field to carry the received, amplified, filtered, and digitized ultrasound echo signals in the receive (US-Rx) mode. Ultrasonic and real-time Doppler images will be constructed outside of the body representative of the anatomy and blood flow within the wICUS array?s field of view. The proposed wICUS technology can be an essential tool for understanding and analyzing physical properties and morphology of the normal and abnormal brain tissue in situ and over time, invaluable for biological, preclinical and clinical research applications.